ISO 639-1 Language Code Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching iso 639-1 language code, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# ISO 639-1 Language Code
# ReDoS-safe | RegexVault — Localization > Locale & Language

import re

iso_6391_language_code_pattern = re.compile(r'^[a-z]{2}$')

def validate_iso_6391_language_code(value: str) -> bool:
    return bool(iso_6391_language_code_pattern.fullmatch(value))

# Example
print(validate_iso_6391_language_code("en"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Locale & Language category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

ISO 639-1 codes are always lowercase 2 letters. Examples: en=English, zh=Chinese, es=Spanish, ar=Arabic, hi=Hindi, ja=Japanese, ko=Korean. Not all languages have ISO 639-1 codes — use ISO 639-3 (3-char) for less common languages.